Kudzu (Pueraria montana var. lobata) – Historical Profile

Written by: Brandon Holden, Alison Kilpatrick, Jonathan Sukhra, Lily Vuong

Canadian Kudzu population along the shores of Lake Erie
Canadian Kudzu population along the shores of Lake Erie near Leamington, Ontairo. Photo courtesy of Mike Cowbrough (Cowbrough, 2016).

HISTORICAL PROFILE

 The history of Kudzu, Pueraria montana var. lobata, started off in eastern Asia in primarily subtropical and temperate regions. The kudzu plant was introduced to the United States from Japan in 1876 at the Centennial Exposition in Philadelphia. The vine was widely marketed in the Southeast as an ornamental plant to be used to shade porches and later promoted as a forage crop (McGroarty, 2010). Concerns revolving around soil erosion through the 1930s and 1940s led the United States Department of Agriculture (USDA) to recommend the planting of Kudzu as a preventative measure along steep slopes throughout the south (Forseth & Innis, 2004). The Soil Erosion Service, a subsection of the USDA went on to provide approximately 85 million Kudzu seedlings to southern farmers, and paid them to plant the seedlings as a means to further prevent soil erosion throughout the Southern United States (Forseth & Innis, 2004; Grebner, Ezell, Prevost, & Gaddis, 2011). These activities were supplemented through a civilian corps movement that encouraged the planting of the vine in public lands and parks (Forseth & Innis, 2004). Due to governmental promotion, Kudzu had a solid hold throughout the Southeastern United States by the early 1950’s (Grebner et al., 2011). Even though Kudzu was removed from the list of permissible cover plants by 1953 (Grebner et al., 2011), declared a weed by 1970 (Hinman, 2011) and finally added to the noxious weeds list by 1997  (Grebner et al., 2011), the plant was able to spread throughout America and has made its way across the border into Canada. Kudzu is currently found on every continent with the exception of Antarctica (Gigon, Pron, & Buholzer, 2014 ).

In Canada, kudzu was discovered near Leamington, Ontario in 2009 and the population was estimated to be at least 8 years old at the time (Lindgren et al., 2013). It is not currently regulated as a pest under any legislation in Canada (Lindgren et al., 2013), nor does it have an official status as a noxious weed under the Weed Control Act (Waldron, 2012).

In  the United States, kudzu has been able to quickly grow over and shade other vegetation, causing damage to crops, orchards, and forest plantations. The greatest monetary impact of kudzu growth has been felt by the forestry industry where the productivity losses of entire young forest plantations have been estimated between $100 million and $500 million per year (Lindgren et al., 2013). There is also concern that kudzu can host soybean rust (Phakopsora pachyrhizi), and crop damage and yield losses have been a problem for farmers (Lindgren et al., 2013). In the United States, kudzu has damaged power lines which costs power companies an estimated $1.5 million per year (Lindgren et al., 2013). Kudzu has also reportedly grown over rail lines and caused derailments, costing railroad companies a significant amount in control costs (Lindgren et al., 2013). Costs of control in national and state parks are also reported to be considerable (Lindgren et al., 2013).

Using climate suitability models of current and future climate conditions, it has been predicted that changes in the global climate will allow for kudzu to spread northward (Lindgren et al., 2013). Waldron (2012) believes that it is likely that the kudzu population near Leamington, Ontario will spread further into southern Ontario unless measures are taken to control it.

ECOLOGICAL CONNECTIONS

 Kudzu is a specialized plant that will grow in certain conditions, thriving to r-strat_animal_yellowunmanageable states if presented ideal conditions, and if found in locations where survivorship is low, could take years for seeds to germinate (Lindgren, C. J. et al). Kudzu’s ability to rapidly grow and take over a deciduous forest canopy stand can surpass any healthy forest ecosystem’s tree growth. It is possible for the vine to have multiple canopy layers that can total the entire biomass of a deciduous forest canopy (Forseth & Innis, 2004).  Kudzu’s resilience to methods of eradication is strongly based on its large roots which store large amounts of starch, nitrogen, and water. The roots proficiency to grow into the substrate at 0.03 metres in depth a day, weighing over 180 kg and extending as deep as 3 metres is only one of many factors associated with the persistence of this plant (Forseth & Innis, 2004). This vine also has the ability to maneuver and redirect its leaf angles in relation to the direction of the sun; this is called paraheliotropism (Forseth & Innis, 2004). The leaves can be in positions to receive full sun, parallel to the sunrays to lower temperatures, and steep angles to prevent wilting (Lindgren et al., 2013). Kudzu’s adaptive qualities threaten local biodiversity through high competition for expanding room and below ground for roots. Studies have suggested that some of the common methods for controlling invasive vines, such as mowing, may be inadvertently causing the plants to grow back even more aggressively, which is something to consider when exploring management options (Kartzinel, Hamrick, Wang, Bowsher, Quigley, 2015). Kudzu is also a ‘structural parasite,’ meaning that, rather than supporting itself, it grows on top of other plants and buildings to reach light. Its ability to reproduce and spread quickly allows it to quickly cover shrubs, trees, and forests, where it blocks the sun’s rays from the plants below it, decreasing or eliminating their photosynthetic productivity (Miller & True, 1986).

CRITICAL ASSESSMENT OF MANAGEMENT OPTIONS

 The invasion of kudzu has proven to be costly to many industries in North America. With Kudzu being relatively new to Canada, and currently limited to a single outbreak, there is still a high probability that an effective management strategy can be implemented to control and eventually eradicate the vine from Canadian Shores. Some of the management options include doing nothing, grazing, chemical control, biological control, prescribed burning, and mechanical removal. These options are considered and assessed based on costs, benefits, and additional factors. Each option is explored in the following paragraphs and compared in Table 1.

There is the option to do nothing, however, seeing as kudzu is predicted to expand its range, this is not recommended. Kudzu will continue to be a burden on many industries if management of the species is not addressed. It may, however, be viable to focus efforts in controlling kudzu by utilizing it rather than removing it. One of these control measures is grazing by livestock. If heavily grazed on for 3-4 growing seasons, the root systems starve and this may effectively eliminate a kudzu population (Starr et al. 1999). However, vines can grow over fences and up trees, rendering them inaccessible to livestock (Lindgren et al., 2013).

A method used to manage kudzu populations is an herbicide called Glyphosate. In Mississippi, Glyphosate was used to tame kudzu and was successful in controlling 60-85% of the vine after 4 years (Lindgren et al., 2013). In some other states, regular use of Glyphosate with a backpack sprayer saw results of 80-100% success in just one season of use. Although herbicides have been effective against kudzu, it requires multiple and frequent applications (Minogue, Enloe, Osiecka, Lauer, 2011). Studies have shown that kudzu that has been controlled with herbicides, and shows no signs of growth, can emerge from its roots after a year, possibly more, of dormancy (Minogue et al., 2011). Some herbicide treatments have left the soil bare, making it difficult to reestablish native species, and does not halt the return of kudzu as it has no problem growing in disturbed areas (Minogue et al., 2011). In some cases, herbaceous species have been able to colonize areas where kudzu has been reduced chemically, however kudzu can return and overtop these species in a single growing season if the area is not closely monitored (Minogue et al., 2011).

Another form of control is prescribed burning. This process kills the foliage of the plant but also requires repeated applications to be effective (Starr, Martz, Loope, 1999).

There are several biological means that are already in place and more that may be implemented to control the growth of kudzu. Bacterial blights, insect herbivory, and insect seed predation occur in high levels in field populations of kudzu. Seed predation is quite prevalent, with up to 81% of seeds incurring damage in populations studied in North Carolina.  A study found two weevils that attacked the stems of kudzu and eight beetles that complete larval development in the kudzu roots. When evaluations of potential control agents are made, the range of the control agents must be considered. Efforts were made by the United States Forestry Service to find a biological control agent for kudzu. A “blackleg” fungus, a viral mosaic disease and a rust fungus have all been shown to cause mild injury to kudzu (Starr et al. 1999). Studies in China revealed that most of these biological control agents do not solely target kudzu, which is a risk to native species (Lindgren et al., 2013). More research needs to be done to determine the viability of biological control options.

Successful long term control of kudzu requires that the extensive root system be destroyed (Starr et al. 1999). As such, the mechanical removal of the entire root has proven to be effective in eradicating the species but is labour-intensive and time consuming (Starr et al. 1999). Another physical control method is close mowing but this requires frequent and repeated action (Starr et al. 1999). Close mowing has the same issues that grazing has as a control method because vines can grow up surfaces, which still requires alternative labour-intensive mechanical removal.

Table 1: Comparison of different potential management methods to deal with the invasive vine Kudzu. While time intensive, mechanical removal provides the greatest chance of success while reducing further negative impact on the environment.

Chart comparing the different Kudzu management method outlined above.

 

References

Cowbrough, Mike. (2016) Photo: Canadian Kudzu population, Lake Erie.

Forseth, I. N. Jr., & Innis, A. F. (2004). Kudzu (pueraria montana): History, physiology, and ecology combine to make a major ecosystem threat. Critical Reviews in Plant Sciences. 23(5):401-413

Gigon, A., Pron, S., & Buholzer, S. (2014). Ecology and distribution of the Southeast Asian

invasive liana Kudzu, Pueraria lobata (Fabaceae), in Southern Switzerland. EPPP Bulletin, 44(3), 490-501. Doi: 10.1111/epp.12171

Grebner, D. L., Ezell, A. W., Prevost, J. D., & Gaddis, D. A. (2011). Kudzu control and impact on monetary returns to non-industrial private forest landowners in Mississippi. Journal Of Sustainable Forestry, 30(3), 204-223. doi:10.1080/10549811.2011.530559

Hinman, K. (2011). Kudzu: how a wonder vine unveiled by Japan at the 1876 centennial began    eating America. American History, (2), 38.

Kartzinel, T. R., Hamrick, J. L., Chongyun, W., Bowsher, A. W., & Quigley, B. P. (2015).          Heterogeneity of clonal patterns among patches of kudzu, pueraria montana var. lobata, an invasive plant. Annals Of Botany, 116(5), 739-750. doi:10.1093/aob/mcv117

Lindgren, C. J., Castro, K.L., Coiner, H. A., Nurse, R. E., & Darbyshire, S. J. (2013). The biology of invasive alien plants in Canada (12): Pueraria montana var. lobata (Willd.) Sanjappa & Predeep. Canadian Journal of Plant Science. 93:71-95, doi:10.4141/cjps2012-128

McGroarty, M. J. (2010). How to control kudzu, the vine that ate the South. Kudzu’’ Retrieved from: http://www.freeplants.com/kudzu.html

Miller, J. H., & True, R. E. (1986). Herbicide tests for kudzu eradication. Georgia Forest Research Paper. Retrieved from https://www.srs.fs.usda.gov/pubs/misc/rp_gf065.pdf

Minogue, P. J., Enloe, S. F., Osiecka, A., & Lauer, D. K. (2011). Comparison of aminocyclopyrachlor to common herbicides for kudzu (pueraria montana) management. Invasive Plant Science and Management. 4:419-426

Starr, F., Martz, K., Loope, L. (1999). Kudzu (pueraria lobata): An alien plant report. United States Geological Survey Resources Division. Retrieved from http://www.hear.org/species/reports/puelob_fskm_awwa_report.pdf

Waldron, G. E., & Larson, B. M. H. (2012). Kudzu vine, pueraria montana, adventive in Southern Ontario. Canadian Field-Naturalist. 162(1):31-33

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English Ivy (Hedera helix), Lily of the Valley (Convallaria majalis), Goutweed (Aegopodium podagraria) and Periwinkle (Vinca minor)- Controlled Burn Management Strategy

By: Christopher Aultman, Dylan Henry, Charlotte Leivo

Controlled Burn Management Plan

The following plan designed to research the potential effects controlled burns has on areas overgrow by common invasive ground covers, including Periwinkle and Goutweed. At the moment, there is little research done on how fire can be used to manage these two plants (Stone, 2009). During a controlled burn, the emerging foliage section of the plants will easily be burnt and destroyed. The question that needs to be researched is, can fire destroy the underground root systems of the plants, and at what temperature does the fire need to be to do so. Due to Periwinkle and Goutweed having an aggressive reproductive strategy of underground runners, even if the above ground portion is burnt, the plants can re-establish and recolonize the area. The intensity of the fire influences the species composition that re-establishes after the fire disturbs the area. As the intensity of the fire increases, the number of species decreases (Heydari, Faramarzi, Pothier, 2016). A study on Longleaf Pine (Pinus palustrisin) showed that high intensity fires that heat the ground to 50℃ and above, have a negative effect on the seeds and cells of the vegetation in the soil, (Gagnon, Passmore, Slocum, Myers, Harms, Platt, Paine, 2015). Fire is a natural disturbance on grassland ecosystems, recreating this disturbance through controlled burns is beneficial. These benefits including increasing nutrient availability, decreasing biomass, controlling insects and diseases, and fire is necessary for some specie’s seeds to germinate (MNRF 2016). The following paragraphs will cover the legal factors, the necessary steps to carry out the plan, and any challenges and the solutions.Controlled_Burn

Photo Credit To: Haunani Thunell

Legal Factors

For this management plan, the Forest Fire Prevention Act is important for controlled burns. Sections 1, 2, 4, and 12 cover when fires can be started, restrictions and permissions when starting a fire, and exceptions for clearing land in a forest area. Small scale fires, small area of grass less than 1 ha, are covered under the Forest Fire Prevention Act Outdoor Fires Reg. 207/96 and are not considered prescribed burns; therefore not needing to be approved by the Ministry of Natural Resources and Forestry (MNRF 2016). However on a large scale, greater than 1 ha, a complexity application is needed to be filed out and submitted to the local  Forest Fire and Emergency Services (AFFES) office within 6 months of the burn. After approval, a burn plan will need to be submitted 60 days before the planned burn date (MNRF 2016).

Carrying out the plan

The first step for this management plan is to determine the study areas. EDDMaps can be used to narrow down the area and then field observation can locate the key areas. The study area will then need to be measured to determine whether the burn will be considered a small outdoor fire or a prescribed burn (MNRF 2016). After that has been determined a data collection plan can be established and the necessary permits and applications can be acquired. Before the burn can be done, a burn plan must be created for the different fire intensities and a timeline must be created for observing if the populations of Periwinkle (Vinca minor) and Goutweed (Aegopodium podagraria) re-establish. A final report with the results of the burns can be made for future management plans.

A proper controlled burn has fireguards. Fireguards are the boundaries of the burn area, and prevent the spread of a fire under control. Fireguard can include waterways bluffs, bare soil, and mowed vegetation that is wet. Large woody vegetation should be placed away from the fireguards in the middle of the area, because they burn hotter, longer and create sparks. The day before the burn gather weather information, low winds makes the fire unpredictable and very high winds make controlling the fire more difficult. A mild constant wind around 8-24 km/hour in one direction is optimal. The local fire department should also be contacted the day before the fire to inform them about the burn (Porter, 2000).

Challenges and solutions

The main challenge for this plan is safety. Fires can be dangerous and spread very easily, which can threaten lives and cause damages to third parties. To combat these issues, being prepared with proper staff and equipment is necessary. All legal requirements can be found in Forest Fire Prevention Act Outdoor Fires Reg. 207/96 sections 1, 2, 4, and 12. A responsible person must be present at all times until the fire is extinguished, and fire extinguishers are necessary. Another challenge of this management plan is length and preparation time for burns that the MNRF consider to be prescribed burns. From the start of the approval process, there is a minimum time of 8 months before the burn date is scheduled (MNRF 2016). This time line cannot be avoided but having a detailed and organized plan set up ahead of time will cut back on any further issues from happening. Another challenge for controlled burns is proximity to homes and other buildings. The solution for this challenge is knowing the municipal bylaw for open air fires/controlled burns, of the area that you will be burning. For example, the City of Mississauga By-Law #49-03 Part II, 7. (1)(b) stats that the permit holder shall not set or maintain an open air fire in a distance less than 50 meters form a building, structure, property line, roadway etc.  Individual municipal bylaws may vary and should be checked before the burn.

Conclusion

The use of fire as a management strategy for invasive ground cover, focusing on Periwinkle (Vinca minor) and Goutweed (Aegopodium podagraria), is a work in progress. The data collected in this plan will be beneficial to future projects and will be a foundation to other management plans. By following the Forest Fire Prevention Act, applying for permits, and creating a burn plan, fire can be a useful and affective management strategy when implemented on the right species; that is why research on Periwinkle and Goutweed is important.

References
City of Mississauga, (2003) By-Law Number 49-03, A by-law to regulate the setting of open air fires and to repeal By-law 60-96, retrieved on March 30, 2017, from http://www.mississauga.ca/file/COM/Open_Air_Burning.PDF
Forest Fires Prevention Act, Outdoor Fires Reg. 207/96 (2016) e-Laws, sections (1)(2)(4)(12) Retrieved from https://www.ontario.ca/laws/regulation/960207
Gagnon, P. R., Passmore, H. A., Slocum, M., Myers, J. A., Harms, K. E., Platt, W. J., & Paine, C.T. (2015). Fuels and fires influence vegetation via above- and belowground pathways in a high-diversity plant community. Journal Of Ecology103(4), 1009-1019. doi:10.1111/1365-2745.12421
Heydari, M., Faramarzi, M., & Pothier, D. (2016). Post-fire recovery of herbaceous species composition and diversity, and soil quality indicators one year after wildfire in a semi-arid oak woodland. Ecological Engineering, 94688-697. doi:10.1016/j.ecoleng.2016.05.032
MNRF (2016) Prescribed burn, Government of Ontario, Retrieved on March 17, 2017, from https://www.ontario.ca/page/prescribed-burn#section-2
Porter M., (2000) How to Conduct a Prescribed Burn, The Samuel Roberts Noble Foundation, Retrieved on March 17, 2017, from https://www.noble.org/news/publications/ag-news-and-views/2000/february/how-to-conduct-a-prescribed-burn/
Stone, Katharine R. 2009. Vinca major, V. minor. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [2017, February 10].

WATER HYACINTH, (EICHHORNIA CRASSIPES) & WATER LETTUCE, (PISTIA STRATIOTES) HISTORICAL PROFILE

Written by: Reid Van Kuren, Andrew Base & Arden Ehrenberg

Historical Profile of Water Hyacinth, (Eichhornia crassipes) :

The origins and expansion of Water Hyacinth, (Eichhornia crassipes) are largely agreed upon by experts as having expanded from tropical South America (Kaufman, 2007). The evidence is not only fossil based or calculated by its preferred habitat, but was clearly recorded through trading documents and expedition journals from the late 1800’s  as natives from the amazon region began to explore and trade with their northern neighbours (Day, 2003). Water Hyacinth plants would be brought along on expeditions to be used for medical purposes. As settlers, explorers, and traders utilized and discarded these plants, the theory is that the plant waste would have been introduced to many aquatic and semi aquatic ecosystems across North America. (Castello, 2010). Some of these areas include the southern states of Texas, Louisiana, and Florida. Since Water Hyacinth’s ideal temperature range is 25-30 °C, these perfect climate conditions, combined with vast water bodies, likely allowed it to spread to water basins not directly visited by travellers. Water Hyacinth is considered extremely aesthetic and was often traded to settlements or offered as prizes (Day, 2003). These are the same criteria which allowed Water Hyacinth to expand to Africa, South Asia, and Australia in the 1880’s, and the Congo and river Nile in the 1950’s. Not only would these areas meet the Water Hyacinth species preferred growing conditions, but would have likely been used for the same purposes since it would have been impossible for Water Hyacinth to naturally disperse that far. (Castello, 2010).

Currently, Water Hyacinth is found around the entire world in both freshwater and salt water locations, often in slow or stagnant water basins. Since it can survive or thrive in the min/max range of 12-35°C, the only places Water Hyacinth is not found are polar and sub-polar regions. For example, Russia, Norway, and most of Canada are too cold for its growth and therefore do not need to worry about its invasive nature. Water Hyacinth has been found in Southern Ontario however, as it shares the same climates as Michigan or Maine.

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Ecological Connections

Water Hyacinth has earned the title as a nuisance species for the same reason as all other pest species – it’s negative and destructive effect on human inhabited areas. While the ideal temperature for Water Hyacinth is 25-30 °C, it can grow rapidly and withstand temperatures as low as 12°C and high as 35°C, meaning it has a broad temperature tolerance.  Water Hyacinth is known as an r-strategist species; it grows rapidly, and as a species it is tough to kill. While not all invasive species are considered nuisance species, Water Hyacinth shares many human-favoured habitats, such as saltwater shorelines, or freshwater rivers, streams, and lakes. The plant has caused problems for boaters, fishermen, and hydro generation as it outcompetes local organisms, gets caught in nets, lines, engines, and water passages (Oyani, 2011).

Water Hyacinth will grow in warm and stagnate or slow moving water, but it can also survive colder and faster moving waters. It may not grow in this situation, but it will survive and it will travel until more favourable conditions are found. Water Hyacinth reproduces using two methods. The first, is its typical r-strategy of reproduction, meaning each plant will send out hundreds of seeds to cultivate in the surrounding ecosystem. Many will die or fail to take root, but some will survive and cultivate, forming new plants along the shore, or in rich soils (Oyani, 2011). The other is its ability to reproduce vegetatively. Rather than rely on seeds, Water Hyacinth will sprout lateral shoots, which form stems, and fan out into new plants creating a mat (Castello, 2010). This process is repeated until all the surface water is covered, or the plant is damaged/destroyed enough to prevent it. If Water Hyacinth is not managed, or there is not a natural hindrance to its growth, the surface mat will eventually block out the sun, preventing underwater species from receiving energy. Once this occurs, photosynthesis decreases, oxygen levels decrease, and underwater organisms will die. Water Hyacinth is also known to choke out shoreline plants.

Assessment of Management Options

There are typically four primary management strategies used to combat Water Hyacinth around the world: Herbicides, machinery, manual removal, and competing species introduction. It is important to note that in nearly all situations and countries around the world, management strategies have failed. Despite research, monetary investment, and various tactics used by multiple governments and industry experts; existing methods have often been insufficient to contain the aggressive propagation of the weed and viability of its seeds.(Gichuki, 2010).

Even though Water Hyacinth can find preferred growth conditions across the equatorial zones, not all cultures have the same opinions or issues with Water Hyacinth. In Brazil for example, there is a local beetle called the N. buchi, which feeds on Water Hyacinth and is able to curtail the spread and reduce its abundance to less destructive levels (Richardson, 2003). By keeping shorelines clear, and allowing patches to form in the mats, aquatic ecosystems can still perform their functions unimpeded. In New Zealand and controlled parts of the U.S., Water Hyacinth is cultivated for medicinal purposes, similar to the pioneers of the late 1800’s, but on a much grander scale (Richardson, 2003).

For areas without a natural management option, the effects of Water Hyacinth can be much more severe. In Kenya, local fisherman and boaters require passage and the ability to fish for their livelihoods and survival. The government there has spent millions building and using machines to “chew up” the mats of Water Hyacinth, but these efforts have failed as the plants regrow and expand too quickly, and the costs of the operations become too much to be worthwhile (Oyani, 2011). There has not been a proven management strategy yet in Kenya.

Regarding herbicide, pesticide, and other chemical use; this method is considered cheaper, but also risks degrading soil and water quality through contamination, and risks bioaccumulation. Different chemicals such as Glyphosate and 4-D acid have been used in Ontario, but due to the volume and resilience of Water Hyacinth, the use of chemicals cannot keep up with the spread of this water weed (Gichuki, 2010). While the results are effective and immediate, the adverse effects on other organisms is often too great a risk.

Perhaps one of the biggest failures in management practices is the lack of cooperation and unification among communities. Despite being a banned aquatic species across the United States, Africa, and other countries – Water Hyacinth is still grown recreationally in private ponds, or sold in nurseries (CLOC, 2015). The combination of the above failures, mixed with the unwillingness from the community suggests another management option: do nothing. For the time being, Water Hyacinth may be a species that is best dealt with by accepting its resilience, and only taking action in the most required or extreme cases where the most harm is occurring.

Table 2. Management methods and evaluations for  Water Hyacinth

Management Method Direct Costs Benefits Drawbacks Efficacy
No Action N/A N/A Continued spread and nuisance.
Herbicides & Chemicals $ Targeted eradication. Contamination, and reduced water and soil quality. +
Manual Removal $ Safest route. Confirmed removal of species. Not effective. Species will regrow too quickly, or return. +
Machine Removal $$$ Quick and efficient. Environmental damage, costly, ineffective. +/-
Alternative Species $$ Natural and effective control of species. Unintended consequences, i.e. damage to other species or ecosystems. ++/–

Historical Profile of Water Lettuce, (Pistia stratiotes)

Historically, water lettuce has become widely distributed throughout the world due to its wide range of use as an ancient medicine, and as such, it is believed that it had been brought along with migrating human populations as they moved from one region of the world to another (Sculthorpe, 1971). Being a plant that reproduces vigorously in tropical and sub-tropical climates, it quickly spread and established large colonies once introduced to areas where it could easily sustain itself. Likely originating from Africa and South America, the water lettuce soon began to establish itself in Central Asia, South East Asia, most Oceanian Countries, southern Europe and finally in Central America along with parts of North America (Langeland, 1998) (EddMaps, 2017). This is largely due to the increase in commercial shipping, as it is hypothesised that cargo ships had the potential to carry water lettuce seeds in their ballasts (OFAH/OMNR, 2012), resulting in the wide dispersion of this aquatic plant species. Eventually, people began to use this plant decoratively in theirs garden gardens, aquariums and ponds, further exacerbating the spread of this plant beyond the sub-tropical range that it had previously occupied.

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Currently, the presence of P. stratoites is recorded in the northeastern region of the United States and in southern Ontario. This eventual migration northward has been recorded in “ponds connected to the Rideau Canal near Ottawa, and in the Welland Canal in the Niagara Region, Lake St. Clair and its tributaries, Bronte Creek in Oakville, and beaches east of Toronto” (OFAH/OMNR, 2012). In addition, its current distribution is also partially due to warming temperatures, and milder winters.

Since the P. stratiotes is not listed on the Invasive Species Act as a regulated or restricted plant, it is common for aquarium and pond stores to sell them. In fact, according to a study conducted near Lake Erie and Lake Ontario, 20% of aquarium and pet stores carried P. stratiotes (Rixon et al, 2005). This contributes greatly to its current spread, as owners of ponds and aquariums may improperly dispose of the plants, which may end up in the Great Lakes or their watersheds. Listed as having an extensive invasion history, according to the Great Lakes Aquatic Nonindigenous Species Information System (GLANIS) water lettuce has a “moderate probability of establishment if introduced to the Great Lakes” (Baker, 2015).

Ecological Connections

As it is known that water lettuce forms dense mats within water ways, it has strong potential to clog them, making recreational activities such as swimming fishing and boating difficult. In areas where water lettuce have formed these large mats, it also blocks out sunlight and in turn, reduces the amount of dissolved oxygen within the water. This makes it very difficult for other aquatic species to survive, especially since this plant is known to consume high quantities of nutrients from the water that it floats on. Not only do these large colonies make habitat less suitable for organisms which occupy the aquatic landscape, but they also block access to water for terrestrial animals (Baker, 2015). To add to this, P. stratiotes colonies can reduce water temperatures, reduce pH, and reduce oxygen mixing with surface wind. As a result, due to these limiting factors, P. stratiotes has the ability to kill native plants, fish and other wildlife in the area that it occupies (Attionu, 1976).

Critical Assessment of Management Options

There are several management strategies already put in place for dealing with non-native water lettuce in ecosystems around the world. Such strategies include the physical removal of the plants from their environment, utilizing other organisms who feed on this plant in order to eradicate it, chemically managing the species population through the use herbicides and cultivating the invasive species for commercial use. The success of these methods are all dependent on the particular location of the habitat, and other limiting factors such as accessibility and sensibility of the ecosystem. Figure 3 demonstrates a condensed version of the benefits and drawback of each strategy. The following is a descriptive list of the possible management strategies:

Chemical Control

The use of herbicide is certainly an effective way to eradicate floating plant matter, although since we are dealing with an aquatic ecosystem, the targeted species may not be the only one affected. Common herbicides such as Glyphosate and Diquat can cause massive weed die-off where the subsequent decomposition may end up removing much of the dissolved oxygen from the water (Baker, 2015).

Biological Control

There has been research conducted to determine if biological controls such as specialist herbivores, meaning organisms who require specific habitat requirement, can be used to eradicate or at least lessen population numbers of P. stratiotes. Species such as the water lettuce moth and the water lettuce weevil feet uniquely on this one plant, and have been used to control this plant in areas where it was not native (Cilliers, 1991). Within 12-18 months the South American water lettuce weevil was able to eradicate at least 40% of the water lettuce in Australia, where it was introduced (Harley et al., 1990). The issue with this approach is that introducing foreign species to a new environment has potentially disastrous consequences. It is very difficult to predict how a non-native species will interact with a new environment. This may not be the best approach for controlling water lettuce in southern Ontario.

Physical Control

To put it simply, this involves the physical removal of the floating plant from the ecosystem. This can be dealt with on a smaller scale by using a small boat, a rake and a bucket to collect the plants, or on a larger scale, through the use of mechanical harvesters. This generally makes for an effective management strategy, as it is a relatively non-invasive procedure concerning the health of the ecosystem. A concern with this method is that since removal boats will be passing through water lettuce patches, there is a risk that these vessels may serve as vector for seeds to “hitchhike” on, thus spreading to other locations.

The following video is a demonstration of how easy it is to conduct physical removals of water lettuce and water hyacinth in London, Ontario, at the Westminster pond. The Upper Thames River Conservation Authority monitors local water bodies for invasive species and

Physical Control with an Economical approach

If these plants can be harvested effectively, its nutritional and medicinal benefits could be put towards good use. Water lettuce contain high concentrations of protein, carbohydrates and fiber and is known to have anti-fungal and anti-microbial properties.  If there is no interest in the food or natural medicine market, they can be used to feed livestock as the plant is known to be fed to pigs. There has also been research into the use of this plant as bio-fuel in areas where water lettuce has overwhelmed certain river systems (Mishima et al. 2008).

Table 3. Management methods and evaluations for  Water Lettuce

Management Method Direct Costs Benefits Drawbacks Efficacy
No Action N/A N/A Continued spread and nuisance.  —
Chemical Control $$ Efficient eradication of species. Contamination, and reduced water and soil quality. May be costly if there is a need for remediation. +/–
Biological Control $ Efficient eradication of species at a low cost Unpredictability of the newly introduced species +/–
Physical Control $$$ Quick, efficient and effective. May spread the species to other locations. Costly. +/-
Physical Control with an Economic Approach $$ Quick, efficient and effective. Economic gain from species removal May spread the species to other locations. ++/-

 

Management Plan

This management plan provides detailed information regarding the most effective management option that involves the least risk to the environment and the general population. Based on the benefits outweighing the costs, it is determined that the physical removal of the plant is the most effective option for control, as long as a small, but closed, market can be built around the removal of the water lettuce. In this case, a closed market is a market in which profit is solely made for the progress of the management strategy.  This approach is the most viable method, since as much of the removed water lettuce can be sold as feed for livestock like cows and pigs, or even be used as a biofuel (Mishima, 2008) additive. Money generated from the sales of this plant can be used as a way to provide more funding towards management resources such as labour and equipment. This system does not create an increasing demand for the product, and would therefore does not necessarily create another market for the plant. If the plant was sold for potential medicinal properties after it’s harvested from targeted sites, there could possibility be an increase in demand for the product and would therefore contribute to the spread of water lettuce in southern Ontario. Previously, in Ontario (Azan, 2015) and in the southern United States (Langand, 1998), the physical approach has been implemented and seems to be the main tactic used my organization in North America.

In addition o this approach, the issue must also be addressed from a different angle. Not only does water lettuce need to be removed from bodies of water in southern Ontario, but the driving factor for its introduction to water ways must be diminished. Seeing that water lettuce is most commonly introduced to the natural environment via decorative ponds or aquariums, a public education plan must be set in place in order to engage communities in the prevention of its propagation and to encourage pond and aquarium business’ to stop selling water lettuce. Programs such as volunteer based river clean-up or invasive species bio-blitzes could be organized in partnership with organizations such as the OFAH of Ducks Unlimited. To add to these programs, pubic education nights and conferences can be hosted, along with efforts to build public pressure upon local governments to take action against the newly emerging invasive species. Strong social media can also reach many targeted interest groups across a broad platform.

Legal Factors

There are no laws conflicting with the physical removal of the invasive species, as it does not negatively impact the quality of the water that the invasive species resides in. Though in order to put more pressure on local and provincial governments to take action, the Clean Water Act (S.O. 2006, Chapter22) can be used as a stepping-stone towards involving communities in the management project. This act requires communities to monitor existing and possible threats to waterways, and to implement necessary actions to diminish the threat. It allows for public participation on all levels, in order for everyone to get the opportunity to play a role in the planning process of any mitigation or prevention plan against the invasion of water lettuce for example. Finally, and most importantly, the Clean Water Act of Ontario requires that all plans and projects must be “based on sound science” (Clean Water Act, 2006). In turn, the Provincial government of Ontario will have more reason to add water lettuce to the Invasive Species Act’s list of invasive species.

Potential Challenges and Solutions

Even if this management project may seem simple and small in scale compared to other efforts focusing on more prominent invasive species, such as giant hogweed and asian carp, this plan still faces many challenges. Most importantly, the issue of funding poses as the largest hurdle in this project. Without any form of income or outside support, no action can be taken against the spread of water lettuce in the waterways of southern Ontario. Secondly, industry that supplies water lettuce is to root cause of its current spread throughout natural water bodies in our region. Actions must be put in place in order to limit the sale of, or at least discourage these industries from selling water lettuce. Finally, in order to highlight the importance of the current issue facing water lettuce in southern Ontario, public knowledge and education programs must be put in place. This will prove to be one of the most important factors that will allow us to reduce the dispersal of the invasive aquatic plant. The following graph highlights the issues, their challenges and the potential solutions that are suggested in order to effectively coordinate a management strategy against the spread of water lettuce.

Table 3. Funding, public awareness of the issue and the water lettuce industry are the most prominent issues facing the management of water lettuce in Ontario.

Issues Challenges Solutions
Funding The challenge is finding the funding to pay for labour, equipment and other necessary resources required for managing the invasive species. -Selling collected water lettuce as biofuel or even as live stock feed.

-Running volunteer and community based programs in order to deal with the issue in a cost effective manner.

-Gain support from local government, in order to receive funding.

-Apply for grants.

The Water Lettuce Industry The decorative pond and aquarium industry is largely the reason whywater lettuce has spread so much in southern Ontario. The sale of this plant is not under any form of control. -Educate the general public about the issue.

– Social pressure from communities for stores to halt the sale of water lettuce may be effective on the small scale.

-Lobbying to add the plant on the Prohibited List of the Invasive Species Act would have the largest impact.

Lack of Public Knowledge Reaching out to a broad range of individuals may prove difficult. Engaging communities may be even more difficult to accomplish -Hold conferences

-Organize shoreline clean-ups and bioblitzes

-Develop a strong media presence.

-Develop partnerships with organizations such as Ducks unlimited or OFAH.

 

 

Conclusion

The physical removal of water lettuce paired with the establishment of a public education program is the ideal method for addressing the spread of water lettuce. This multi-faceted approach tackles the current issues that water ways in Southern Ontario face in regards to water lettuce, and also addresses the main source of the spread of the plant. Since this plan involves sound scientific research, community involvement and sound ecological practices, this management plan will ideally be successful upon its undertaking.

 

References

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Cilliers, C.J. (1991). Biological control of water lettuce, Pistia stratiotes (Araceae), in South Africa. Agriculture, Ecosystems, and Environment 37(1-3): 225-229.

Day J, Bianchi T, et al. (2003). Water Hyacinth Origins. Gulf Of Mexico Origin, Waters, and Biota : Volume 4, Ecosystem-Based Management. 83-88. College Station: Texas A&M University Press.

Evans, J.M. 2013. Pistia stratiotes L. in the Florida Peninsula: biogeographic evidence     and conservation implications of native tenure for an ‘invasive’ aquatic plant.     Conservation and Society 11(3):233-246.

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Harley, K.L.S., R.C. Kassulke, D.P.A. Sands, and M.D. Day. (1990). Biological control of water lettuce, Pistia stratiotes (Araceae) by Neohydronomus affinis (Coleoptera: Curculionidae). Entomophaga 35(3): 363-374.

Kaufman, S.R. (2007). Invasive Plants: Guide to Identification and the Impacts of             Control of Common North America Species. Stackpole Books.

Langeland, K.A., and K.C. Burks. 1998. Identification and biology of non-native plants in Florida’s natural areas, p. 20. University of Florida. Gainesville, FL.

Mishima, D., M. Kuniki, K. Sei, S. Soda, M. Ike, and M. Fujita. (2008). Ethanol production from candidate energy crops: Water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes L.). Bioresource Technology 99: 2495-2500.

Richardson, J (2003). Weevils save lakes from water hyacinth pest. Ecological Economics, 45 (105-106). https://www.newscientist.com/article/dn3703-weevils-save-lakes-from-water-hyacinth-pest/

Rixon, C.A.M., I.C. Duggan, N.M.N. Bergeron, A. Ricciardi, and H.J. MacIsaac. 2005. Invasion risks posed by the aquarium trade and live fish markets on the Laurentian Great Lakes. Biodiversity and Conservation 14: 1365-1381.

OFAH/OMNR Invading Species Awareness Program. (2012). Water Lettuce. Retrieved from: http://www.invadingspecies.com.

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Langeland, K.A., and K.C. Burks. 1998. Identification and biology of non-native plants in Florida’s natural           areas, p. 20. University of Florida. Gainesville, FL.

Mishima, D., M. Kuniki, K. Sei, S. Soda, M. Ike, and M. Fujita. (2008). Ethanol production from candidate           energy crops: Water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes L.). Bioresource Technology 99: 2495-2500.

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English Ivy (Hedera helix), Lily of the Valley (Convallaria majalis), Goutweed (Aegopodium podagraria) and Periwinkle (Vinca minor)-Historical Profile

By: Christopher Aultman, Dylan Henry, Charlotte Leivo

History:

The following paragraphs will go into detail about the early records, uses and likely reason that contributed to the popularity and naturalization of the following groundcover species: English Ivy (Hedera helix), Lily of the Valley (Convallaria majalis), Goutweed (Aegopodium podagraria) and Periwinkle (Vinca minor).

English Ivy, Hedera helix, has been widely used by early Europeans as an insulator on stone buildings throughout the year (Sternberg, Viles, Cathersides, & Edwards, 2010). This may have had a large impact on English Ivy being imported to North America, with early records placing the plant in Virginia by 1762 (Wells & Brown 2000). The plant later became widely used for aesthetic purposes instead of as an insulator with the change of heating systems and house design (Sternberg, Viles, Cathersides, & Edwards 2010). The horticulture industry utilized the appeal of this plant to sell and distribute the ivy across North America, with the American Ivy Society widely promoting it currently (Waggy, 2010). Despite the horticulture industry’s success with selling English Ivy, it is having a profoundly negative impact on the natural ecosystem. The ivy was used for erosion control in the 1900’s which may have contributed to the plant’s establishment in many areas across United States. Birds also contribute to the dispersal of the seeds (Waggy, 2010). These factors have likely contributed to the plant negatively impacting the forestry industry by disrupting the growth patterns of the forest, which indirectly impacts the local distribution of the animal species (Waggy, 2010).

Lily of the Valley, Convallaria majalis, has been widely depicted in ancient lore with associations to the Virgin Mary being called Our Lady’s Tears and the virgin goddess of Ostara in Germany when they were pagans. (World of flowering plants, 2014) The plant was further used in a wine concoction to treat various ailments leading to the liquid being known as “Golden Water”. (Haas, N.D) These deeply rooted legends and uses in the culture of early Europeans may have lead to the plant being widely cultivated in North America. The American Gardening book indicates that Lily of the Valley was exclusively imported from Germany in the 1800’s. (Bailey, 1894) As time progress the plant was recommended to be planted for numerous hardy conditions where no other exotic plants would survive. (Bailey, 1894) This plant then escaped cultivation, becoming naturalized in native ecosystem and having the same effect on the landscape as the other groundcovers.

Goutweed, Aegopodium podagraria, was brought over by colonial settlers to America with early records placing it in North America since the 1850’s. (Waggy, 2010) Historically, goutweed was used for food and for its medicinal properties in treating gout, in many European countries, this was likely the reason behind bring the plant to North America. (Waggy, 2010) Goutweed is now being grown as an ornamental groundcover because of its rapid growth rate and hardiness in many environments. Nurseries throughout North America have widely promoted the plant for this use. (Waggy, 2010) As people became more irritated with the plant outcompeting the other plants in the garden people have disposed of the plant in various forests to be rid of the plant. (Waggy, 2010) This is now creating problems for the overall health of ecosystems and is getting the attention of the forestry industry and other natural groups.

Like goutweed, periwinkle was likely brought over initially for its edibility by early European settlers. Early records indicate that periwinkle has been in Virginia since 1771(Wells & Brown, 2000)  but may have been in North America earlier than this. The range of periwinkle is due to the horticulture industry, in the American Gardening book periwinkle was recommended on numerous accounts to be used for erosion control along the riparian zone (Bailey, 1894). This could have impacted the naturalization of the plant in native ecosystems in North America. As time progressed the plant was widely distributed and sold in many greenhouses and nurseries in North America for its gorgeous blue flowers and tolerance for shade (Stone, 2009). It is likely that periwinkle escaped cultivation from homes that bordered forested ecosystems (Darcy & Burkart, 2002), bringing rise to problems in the environment.

Ecological Connections:

The reproductive strategies deployed by the following groundcovers; Goutweed, Lily of the Valley, English Ivy, and Periwinkle have contributed to the successful establishment of the natural environment. Once in an ecosystem the rapid expansion by vegetative growth allowed the groundcovers to quickly form dense mats on the forest floor. This resulted in outcompeting native plant species and restricting available sunlight  that killed germinating native flora, including tree species (Waggy, 2010. Stone, 2009. Darcy & Burkart, 2002). The ability of English Ivy to grow vertically on trees and the use of adventitious roots allows it to create what is known as “Ivy deserts” in a forest as it affects all strata of a forest (Waggy, 2010). The rhizomes of goutweed and lily of the valley allow them to grow in numerous soil and shade conditions. Where then creep inward to areas that their seeds cannot properly germinate. The strong fragrances of these two groundcovers have been known to attract numerous pollinators to their flowers (Waggy, 2010. Ohara, Araki, Yamada, Kawano, 2006).

Other factors that possibly lead to these plants becoming established in an Ecosystem would be disturbed ecosystems. These ecosystems could have become disturbed by different factors. Overabundance of deer within an ecosystem results in the deer over browsing the native flora, which would lead to an open space where these invasive plant species can enter the area (Rawinski, 2008). Once these plants establish they quickly grow out of control unopposed because the deer do not favour these exotic plants. Other factors could be recent fires that disrupted the ecosystem or improper human management of the forest stands.

The negative impacts that the groundcovers have on a forest has recently started to raise concerns with environmental-related organizations and naturalist alike as they are decreasing the biodiversity in these forest ecosystems. As the formation of dense mats on the forest floor are affecting the forest’s ability to replenish varying levels in the canopy layer, weakening the overall health of the forest (Waggy, 2010). The biggest concerns for this comes from Periwinkle and English Ivy based on studies that confirmed they had an incredibly negative effect on the germination and growth of seedlings (Waggy, 2010. Darcy and Burkart, 2002). The high fragrance of goutweed and lily of the valley has gotten naturalists concerned about the pollinator to native plant species interaction, which may lower the seed reproduction of wanted native plant species (Waggy, 2010. Ohara, Araki, Yamada, & Kawano, 2006). Periwinkle, English Ivy and Goutweed have been known to negatively impact riparian zones and floodplains as they widely establish themselves in these areas or were once used as erosion control in these locations (Waggy, 2010). Furthermore, as native plants species begin to disappear in regions native fauna will begin to decrease in areas where these ground covers are taking over the forests.

Critical Assessment of Current Management Strategies:

Introduced invasive plants threaten ecosystems due to their excessive growth and have both ecological and economic impacts. Invasive species threaten native wildlife and ecosystems and are causing ecological havoc in many of our most sensitive habitats, pushing many of our native plants and animals to the brink of extinction (Padullés & Vila & Barriocanal, 2015). Each method option is described in the next paragraphs.

Prevention:

The best way to ultimately control these groundcover species is prevention. This can be achieved by maintaining a healthy ecosystem where these plants cannot establish themselves in. Other methods of preventing these species from invading these natural spaces is to educate the public on ways to ensure the plant cannot spread into these ecosystems. Like not planting these plants on areas that border the ecosystem where they could spread vegetatively or creating deep barriers that the roots would not be able to grow past.However, if the plants have already established themselves in these regions there are the following methods of control: Do nothing, Biological Control, Chemical Control, Mechanical or Physical Control. The following paragraphs will go into detail for the effectiveness of each control for English Ivy, Goutweed, Lily of the Valley, and Periwinkle.

Do Nothing:

Doing nothing is always an approach that can be taken to address this issue. Many people have voiced their opinion on the severity of invasive species establishing themselves in an environment or if it’s just natural and these species are just becoming integrated in the environment. This suggests that if a long enough time passes these plant species will be adopted into the diet of native fauna as some evidence of White-tailed Deer and Volcano Rabbit browsing on Periwinkle (Stone, 2009) is already coming to light. English Ivy is another plant species that has been documented to be incorporated in White-tailed Deer diets (Waggy, 2010). Currently there is no known species that native species that consume lily of the valley or goutweed but it has been noted that many pollinator species are widely attracted to these species and aid in the pollination. However, if these plants are left alone to grow out of control it would completely disrupt many ecological functions in an environment as they spread quickly by rhizomes and will out-compete all layers of a forest by restricting light to tree seedlings or ground flora (Stone, 2003. Waggy, 2010). Several studies focusing on the effects of leaving certain study plots unchecked in Michigan, Illinois, Oregon, Sweden, Czech Republic and the Netherlands indicate that the plant populations exponentially in the environment if unopposed. Resulting in potential losses in the Forestry Industry as wood production in these areas begin to decline without the growth of new trees. Other similar industries that benefit from resources coming from these forest ecosystems may also be negatively impacted.

Biological Control:

Biological control is another control method that proves to be effective in multiple studies that took place in Europe and United States for Goutweed, English Ivy and Periwinkle. One common biological control method for these species are the use of livestock; cattle, goats and sheep to limit or eliminate these species from an environment. In Oregon, a study was performed to look at the effects of goat browsing on English Ivy in managed plots in a forest ecosystem. The study showed that high intensity, short duration browsing of the juvenile stages of English Ivy resulted in the decrease of plant cover to 23% in the 1st year of browsing, and to 4% plant cover in the following year (Ingham & Borman, 2010). A similar study has been performed in New Zealand but substituted with sheep instead of the goat that yielded similar results. Another study done in the Netherlands showed the effects of large cattle browsing in forest ecosystems of bramble and groundcovers. This study showed that the effects of cattle browse and trampling effects on the ecosystem resulted in English Ivy and Periwinkle to disappear in the plot by 2004 despite there being no significant difference in frequency between the ungrazed and grazed plot in 2002 (Van Uytvanck & Hoffman, 2009). A study that was conducted in the Czech Republic, examined the effects of cattle grazing on forb species at a grassland site, the site contained varying intensities of Goutweed. This study revealed that varying intensities of cattle grazing resulted in the vast decrease or disappearance of Goutweed present at the pasture plots (Pavlů, Hejcman, Pavlů, Gaisler, & Nežerková, 2006). Therefore indicating that livestock browsing of all three species can be executed in a forest ecosystem and be effective in managing these invasive groundcovers species, the exception being Lily of the Valley. The study based out of Oregon further indicated that goats could be used within urban parks. (Ingham & Borman, 2010) The management strategy utilizes the agricultural industry to control invasive species in an ecosystem indicating the combined benefits of providing food for livestock that may be used for producing dairy, food, and/or textile products. Making this method cost effective as there is a source of income coming in from the used animal species but could cause other problems as the may consume wanted native flora and could compact the soils depending on the animals used.

Chemical Control:

Chemical control methods may be one of the most commonly used management strategies for large populations of invasive plant species throughout Canada and the United States of America. A study was done in Oregon that indicated performing chemical control on English Ivy in the winter proved to be effective (Waggy, 2010). Further studies completed in New Zealand indicated that basal application after the mature plant was cut proved effective for a short duration (Griffiths, 2010). It has been noted that Goutweed and Periwinkle persist after the use of Glyphosates because of the vegetative growth response following the procedures and the deep rhizomes that likely were not affected by the spraying (Waggy, 2010. Stone, 2009). The same is true for Lily of the Valley because it contains deeply rooted rhizomes that escapes the chemicals (Kosinski, 2003). Therefore proving that the application of herbicides is only a short-term solution to a long-term problem.

physical and mechanical control:

The most common way that many conservation areas remove invasive ground cover like periwinkle and goutweed is by implementing physical and mechanical control methods to remove the plant body and roots (CVC, 2017). This method of removal is only effective if the entire root mass is removed due to rhizomes being able to rapidly recolonize in the soil. If the entire plant is not removed the plant will continues to grow new shoots (CVC, 2017). Excavation can be very affordable if completed  with volunteers and hand tools. However heavy machinery can be used which will increase cost but reduce the duration of the project. In some cases these methods are the only available control methods for invasive plant species that do not utilize chemicals, Lily of the Valley is one of these species. A study done in Poland, simulated the effects an animal would have if they were to consume Lily of the Valley on a yearly basis by continually mowing populations of the plant (Kosinski, 2003). This study was successful in showing that if Lily of the Valley was intensively mowed back and trampled upon, the plant will decrease in vegetative cover (Kosinski, 2003). However, some of these methods may not be effective in a forest ecosystem as it will provide an entry point for new invasive species or will make it so new species cannot regrow in the area this is dependant on the material used to smother the plant. Therefore, indicating that these methods are best used in conjunction of previously mention methods to effectively remove the species or strategies of replanting native plant species in the area immediately following these methods. This method is incredibly physically demanding and involves a lot of labour if done on a larger scale, thus being an ineffective of management due to the high resource need.

Table 1: Illustrates a comparison of doing nothing,biological control, fire management, physical and mechanical control, herbicides and prevention as a method to resolve the invasion of Vinca minor L., Convallaria majalis, Aegopodium podagraria & Hedera helix in North America.

Strategy Cost Benefits Factors Effectiveness
Do Nothing $ Cost Effective Would cost more to maintain landscape with the outspread of targeted species expanding.  Species would continue to thrive and choke out native plants.
Biological Control $$ Effective in natural removal and fertilizing of area. Consumes wanted native plant species. +
Physical and Mechanical Control $$-$$$$ Only targeted species are removed from the area. Can be cheap. Labour intensive. Soil compaction. Disturbed soils could provide suitable germination for other invasives +
Herbicides $$$ Effective initial short-term treatment Plants that are not targeted may also be affected by spray methods
Prevention $ Natural ecosystem restored. Effective in preventing plants initially but does not work if the invasive plants are already present. ++

References

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Darcy, A.J., & Burkart, M.C. (2002). Allelopathic Potential of Vinca minor, an Invasive Exotic Plant in West Michigan Forests. Bios, 73(4), 127-132. Retrieved from http://www.jstor.org/stable/4608646

Griffiths, K. (2010) Control methods of English Ivy in Puahanui Bush, NZ. The Conservation Company LTD. Retrieved from   http://www.theconservationcompany.co.nz/pdf/Control%20methods%20for%20English%20ivy.pdf

Haas, L.F. (N.D). Convallari majalis (lily of the valley) (also known as Our Lady’s tears, ladder to heaven).Journal of Neurology, Neurosurgery & Psychiatry 1995;59:367.

 

Ingham, C. S., & Borman, M. M. (2010). English Ivy (Hedera spp., Araliaceae) Response to Goat Browsing. Invasive Plant Science & Management, 3(2), 178-181. doi:10.1614/IPSM-09-021.1\

Kosinski, I. (2003) The Influence of Shoot Harvesting on the Age Structure of Convallaria majalis L. Populations. Acta Societatis Botanicorum Poloniae (Vol 72). No. 1: 53-59,2003

Ohara, M., Araki, K., Yamada, E., & Kawano, S. (2006). Life-history monographs of Japanese plants. 6: Convallaria keiskei Miq. (Convallariaceae). Plant Species Biology, 21(2), 119-126. doi:10.1111/j.1442-1984.2006.00157.x

Pavlů, V., Hejcman, M., Pavlů, L., Gaisler, J., & Nežerková, P. (2006). Effect of continuous grazing on forage quality, quantity and animal performance. Agriculture, Ecosystems And Environment, 113349-355. doi:10.1016/j.agee.2005.10.010

Padullés Cubino, J., Vila Subirós, J., & Barriocanal Lozano, C. (2015). Propagule pressure from invasive plant species in gardens in low-density suburban areas of the Costa Brava (Spain). Urban Forestry & Urban Greening, 14941-951. doi:10.1016/j.ufug.2015.09.002

Rawinski, T.J. (2008) Impacts of White-Tailed Deer Overabundance in Forest Ecosystems Overview. Forest Service, U.S. Department of Agriculture, Northeastern Area State and Private Forestry. (Producer). Retrieved from https://www.na.fs.fed.us/fhp/special_interests/white_tailed_deer.pdf

Sternberg, T., Viles, H., Cathersides, A., & Edwards, M. (2010). Dust particulate absorption by ivy (Hedera helix L) on historic walls in urban environments. Science Of The Total Environment, 409162-168. doi:10.1016/j.scitotenv.2010.09.022

Stone, K.R (2009) Vinca Major, V, Minor. In: Fire Effects Information System [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Retrieved from http://www.fs.fed.us/database/feis/plants/vines/vinspp/all.html

Vandepitte, K., De Meyer, T., Jacquemyn, H., Roldan-Ruiz, I., & Honnay, O. (2013). The Impact of extensive clonal growth on fine-scale matting patterns: a full paternity analysis of a lily-of-the-valley population (Convallaria majalis). Annals of Botany, 111(4), 623-628

Van Uytvanck, J., & Hoffman, M. (2009) Impact of grazing management with large herbivores on forest ground flora and bramble understory. Acta Oecologia, 35(4):523-532. DOI: 10.106/j.actao.2009.04.001

Waggy, M. A. (2010) Aegopodium podagraria. In: Fire Effects Information System. [Online.] U.S Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Retrieved from https://www.fs.fed.us/database/feis/plants/forb/aegpod/all.html

Waggy, M. A. (2010) Hedera helix. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [2017, February 11].

Wells, E., & Brown R.L. (2000). An Annotated Checklist of the Vascular Plants in the Forest at Historic Mount Vernon, Virginia: A Legacy from the Past. Castanea, 65(4), 242-257. Retrieved from http://www.jstor.org/stable/4034007

World of Flowering Plants (2014) Legends and Facts about the Lily of the Valley. (Online) Retrieved from http://worldoffloweringplants.com/legends-facts-lily-valley/

English Ivy (Hedera helix), Lily of the Valley (Convallaria majalis), Goutweed (Aegopodium podagraria) and Periwinkle (Vinca minor)- Ecological Profile

Written By: Chris Aultman, Dylan Henry, Charlotte Leivo, Annika Young

There are four invasive groundcovers that are becoming an increasing concern in Canada and United States of America, for they are becoming better established within the natural environment: English Ivy (Hedera helix), Goutweed (Aegopodium podagraria), Lily of the Valley (Convallaria majalis), and Periwinkle (Vinca minor).

r-strat_plant_yellow

Distribution

Common invasive groundcover species are Periwinkle (Vinca minor) and Goutweed (Aegopodium podagraria) originate from Eurasia. The two plants now grow in Southern Canada from British Columbia to Southern Ontario, as well as the West coast and East United States. The global distribution of the two invasive plants can be found on Figure 1 and the distribution of the plants in Ontario can be found on figure 2.

Lily of the Valley, Convallaria majalis, originates from Europe and Eurasia (shown in Figure 3).  The species ranges from most States and some of Southern Canada (shown in Figure 2). They were brought to North America by settlers that used this plant for ornamental and medicinal purposes. It is highly toxic to animals, particularly the leaves and each plant has a different amount of toxin called convallatoxin. (Kaufman & Kaufman,2007).

English Ivy, Hedera helix, is an evergreen climbing plant native to Europe, western Asia, and northern Africa (Kaufman & Kaufman, 2007). English Ivy was introduced to North America as a decorative plant starting in the 1700s and is now considered an invasive species (Kaufman & Kaufman, 2007). It is found in 26 states in the United States, southern British Columbia, and southwestern Ontario and has also been introduced to South Africa, India, Australia, New Zealand, Brazil, and Mexico (Kaufman & Kaufman, 2007; Waggy, 2010).

Periwinkle Goutweed Global Distrabution
Figure 1: Global Distribution of Periwinkle (Vinca minor) and Goutweed (Aegopodium podagria) (ArcMap 10.4, EDDMaps 2017, iNaturalist 2017)
Ontario_Common_Invasive_Groundcover
Figure 2: Southern Ontario Distribution of the four Common Invasive Ground Covers, English Ivy (Hedra helix), Goutweed (Aegopodium podagraria), Lily of the Valley(Convallaria majalis), and Periwinkle (Vinca minor) (ArcMap 10.4, EDDMaps, 2017)
lilyofthevalley_global_dist
Figure 3: Global Distribution of Lily of the Valley (Convallaria majalis) (Modified by Invasive plants, 2017 Base map source: ArcMap 10.4)

Habitat

Periwinkle is often found in open forests and around old home-sites as they were favoured by early European settlers for their medicinal properties. (Kaufman, Kaufman. 2012) These

periwinkle

Figure 7: Common Periwinkle, Vinca minor (Zell, 2009 a)

plants can be found in soils that are: Silt loams, Clayey, loamy and sandy soils, and rocky sandy soils. (Stone. 2009) However, they prefer soils that are fertile and moist but can tolerate lowly fertile and moderately to well-drained soil site locations.(Stone, 2009) They further favour soils that are relatively shallow, 5.7-8.7 inches deep, and grow in soils of 5.7-7.2 PH levels. Periwinkle favours partial shade but is known to tolerate full sun and fully shaded areas. (Stone, 2009)

 

Goutweed is often found in moist sites, preferably sites that are moist and well drained within partial shade areas. (Waggy. 2010) These plants are tolerant of floodplains and

goutweed
Figure 8: Goutweed, Aegopodiom podagraria (Peters, 2005)

moisture contents that are 33.2-36.4%. Goutweed is known to be a nitrophilous species, meaning they are indicators of nitrogen rich soils but is more restricted by soil PH levels.
The PH levels they have been known to occur in is 3.1-9 within its native range in Europe. (Waggy, 2010)The soil they seem to prefer are: Sandy loam, silty loam, and sandy clay.
(Waggy, 2010) These species are highly tolerable of highly shaded area where the canopy layer is 90% and seem to prefer thin litter layers to spread. (Waggy, 2010)The areas they are known to first establish within are roadsides, forest edges and disturbed forest floors (Kaufman, Kaufman) before expanding vegetatively into areas that seed germination is not favourable.

Lily of the valley has adapted to grow in a wide range of soils that are acidic and alkaline.

lily_of_the_valley
Figure 9: Lily of the Valley, Convallaria majalis (Zell 2009 b)

(Vandepitte, De Meyer, Jacquemyn, Roldan-Ruiz, & Honnay, 2013)  However, is mainly found within acidic soils in its native range and its non-native range in North America. They thrive within fertile and humic soils (Kaufman, Kaufman) with well drained moist soils. (Vandepitte, De Meyer, Jacquemyn, Roldan-Ruiz, & Honnay) Within its native range it is mainly found in ancient deciduous forest and naturalizes within similar forest types around the world. Studies suggests that it can tolerate coniferous forested sites with highly acidic soils as well as low light conditions but does not perform well under these conditions. (Verstraeten, Baeten, De Frenne, Thomaes, Demey, Muys, & Verheyen. 2014) Further indicating that they can thrive within mix-forested, Carolinian and boreal forests in Canada.

 

The preferred habitat of English Ivy in its native range is floodplains with moist, nutrient-rich substrates (Schnitzler & Heuzé, 2006).

english_ivy
Figure 10: English Ivy, Hedera helix (Chery, 2006)

Its preferred hosts in this environment are large and isolated trees that provide greater surface area for attachment and increased exposure to sunlight (Castagneri, Garbarino, & Nola, 2013). In North America, English Ivy prefers moist areas with full to partial shade but can also tolerate drought (Kaufman & Kaufman, 2007). It has been noted to thrive in disturbed and fragmented forests (Kaufman & Kaufman, 2007; Londré & Schnitzer, 2006). English Ivy is capable of growing in Canadian Hardiness Zones 4a to 8b (Pascoe, 2017).

 

Reproductive Strategy

Organisms can generally be divided into two broad categories of reproductive strategy: r-selection and K-selection. R-strategists have high population growth rates and typically colonize new or disturbed areas, while K-strategists favour efficient use of resources and are typically found in areas where populations are near carrying capacity (Molles & Cahill, 2014). Most species of invasive plants would be expected to be r-strategists. However, despite its preference for colonizing disturbed areas, English Ivy displays two traits associated with K-strategists: longevity and parental investment. English Ivy can live for many decades. Schnitzler and Heuzé (2006) found a specimen in northeast France that was at least 66 years old. Its seeds, rather than being wind-borne, are carried in fruits (Kaufman & Kaufman, 2007). In addition, English Ivy appears to be capable of establishing or persisting in late-successional as well as disturbed communities (Waggy, 2010). English Ivy is therefore closer to being a K-strategist than an r-strategist. Its pattern of survivorship also supports this conclusion. English Ivy can spread via runners, bird-dispersed seeds, or cuttings in contact with earth (Kaufman & Kaufman, 2007).

The primary method of reproduction for Vinca minor and Aegopodium podagraria are underground runners from rootlets (Kaufman, Kaufman, 2007). Both of the species rarely repopulate from seeds. The seeds from Goutweed need very specific conditions to survive after germination, the requirements are recently disturbed soil and a sunny location (CVC, 2017) Both Periwinkle and Goutweed have attributes that make them r-strategist species. The r-strategists attributes the species have are rapid growth rate, and frequent reproduction through the runners and quick to maturity.

Lily of the valley, Convallaria majalis propagates by two methods. During warm months the plant sends out underground stems called rhizomes, which form new upright shoots called stolons. In the spring these grow into new leafy shoots that still remain connected to the other shoots under ground, and often form large colonies. It also produces a small, white, sweetly scented flower that produces a small orange-red berry. The berry contains a few large whitish to brownish colored seeds that dry to a clear translucent round bead. Majalis cannot self fertilize and it is self-sterile, if there are not two colonies available to cross pollinate the plant will not be able to seed. (Chace & Coover, 2012).

Survivorship 

The survivorship of many invasive species are type three, with high mortality at seedling stage of life followed by high rate of survival among the fully grown (Molles, Cahill, 2014) The type three curve fits the survivorship of Periwinkle, Goutweed and Lily of the Valley because of the low chance of seedling for the plants to germinate. However through the reproductive strategy of runners there is a higher chance of surviving due to the main body being established, Figure 3 shows a survivorship curve representing the three survivorship types based on organisms survived over time.

The germination rate of English Ivy seeds is near 100%, especially with the pulp removed via digestion by birds (Biggerstaff & Beck, 2007). Low juvenile mortality suggests either a Type I or II survivorship curve depending on whether mortality rates are greater (Type I) or the same (Type II) among older individuals (Molles & Cahill, 2014).

survivorship_curve
Figure 11: Three Types of Survivorship Curve (Husthwaite, 2009)

Dispersal and Vectors Vector_Human

The primary vector for Common Periwinkle, Goutweed and Lily of the Valley would be humans; Humans either improperly dispose of the garden waste produced by these plants or they plant these groundcovers due to the beautiful flowers produced, easy maintenance and edibility. (Kaufman & Kaufman. 2007) Because of the rhizomes on the roots, the plant can easily be establish in the compost. (CVC, 2017) Due to these plants being widely distributed and sold by plant nurseries and lack of education on the impacts they have ecologically, consumers may plant them on their property were the invasive plants can easily escape into the surrounding environment.(Darcy & Burkart. 2002). Common periwinkle is known to be dispersed throughout its native range by the means of ants (Stone, 2009), it is currently unknown whether or not this occurs in North America. Due to the toxicity of lily of the valley no known species disperse the seeds over a long distance. Goutweeds main dispersal agent is gravity and the wind pushing the seeds a small distance, it is currently unknown if animals aid in the dispersal of ribbed seeds that could adhere onto fur. (Waggy, 2010) Due to the lack of seeds that these plants produce, this prevents any major dispersal over varying distances, however if unchecked the plants can overtake a substantial area through the underground root systems. English Ivy and other invasive groundcovers are still planted in gardens, where they can grow into natural areas(Ontario’s Invading Species Awareness Program, n.d.). The seeds of English Ivy can also be dispersed by birds (Kaufman & Kaufman, 2007).

Special Considerations

The juvenile and adult stages of English Ivy differ greatly in growth form, reproductive capacity, and leaf shape (Castagneri, Garbarino, & Nola, 2013). These differences are summarized in Table 1. The leaves of the adult form have greater total photosynthetic capacity than the leaves of the juvenile form. However, the leaves of the juvenile form are better at adapting to changing light levels due to greater phenotypic plasticity (Bauer & Thöni, 1988). English Ivy has some medicinal uses and is capable of causing contact dermatitis (Kaufman & Kaufman, 2007; Paulsen, Christensen, & Andersen, 2010).

Table 1: Comparison of juvenile and adult Hedera helix. Adapted from Castagneri, Garbarino, & Nola, 2013.

Characteristic Juvenile Adult
Growth Form Prostrate                                             Climbing
Reproductive Capacity Sterile Fertile
Leaf Shape Palmately lobed Unlobed, oval-shaped

Convallaria majalis and Aegopodium podagraria are both non-native to North America and have no known predators in their introduced habitats.  Vinca minor , however has been noted in Illinois to have one known predator, which is White-tailed deer. One consideration of these species is if they are being removed through excavation the entire root mass and all runners should be removed to prevent the organisms from re-establishing. All species have been known in the past to be used for medicinal and ornamental purposes. Lily of the Valley is toxic to most animals.

References

Bauer, H., & Thöni, W. (1988). Photosynthetic light acclimation in fully developed leaves of the juvenile and adult life phases of Hedera helix. Physiologia Plantarum, 73(1), 31-37. doi:10.1111/1399-3054.ep12975682

Biggerstaff, M. S., & Beck, C. W. (2007). Effects of English Ivy (Hedera helix) on Seed Bank Formation and Germination. American Midland Naturalist, 157(2), 250-257.

Castagneri, D., Garbarino, M., & Nola, P. (2013). Host preference and growth patterns of ivy (Hedera helix L.) in a temperate alluvial forest. Plant Ecology, 214(1), 1-9. doi:10.1007/s11258-012-0130-5

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Verstraeten, G., Baeten, L., De Frenne, P., Thomaes, A., Demey, A., Muys, B., & Verheyen, K. (2014). Forest herbs show species-specific responses to variation in light regime on sites with contrasting soil acidity: An experiment mimicking forest conversion scenarios. Basic and Applied Ecology, 15316-325. doi:10.1016/j.baae.2014.05.002

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Image Credits:

chery. (2006, October 16). Hedera helix clinging. Retrieved from https://commons.wikimedia.org/wiki/File:Hedera_helix_clinging.jpg    

Husthwaite, R. (2009, April 23). Survivorship curves. Retrieved from https://commons.wikimedia.org/wiki/File:Survivorship_Curves.jpg

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Peters, K. (2005, July 15). Aegopodium podagraria blatt. Retrieved from https://commons.wikimedia.org/wiki/File:Aegopodium_podagraria_blatt.jpg

Zell, H. (2009a, April 14). Vinca minor 001. Retrieved from https://commons.wikimedia.org/wiki/File:Vinca_minor_001.JPG

Zell, H. (2009b, April 29). Convallaria majalis 0001. Retrieved from https://commons.wikimedia.org/wiki/File:Convallaria_majalis_0001.JPG